Introduction

Learn about what an AtCollection is and ways you can build one.

What are AtCollections?

AtCollections is a typed, shareable, reactive layer on top of AtRecords.

An AtCollection<T> hold a list of CItem<T>, where T is a type that you define. A CItem<T> is a record that wraps your own domain object (a Todo class, a Pet class, a Dart Map, or a plain String). Instead of working with raw AtKey/AtValue pairs, the SDK handles key shapes, per-recipient fan-out, encryption, sync, and event plumbing underneath.

Each collection is scoped to a namespace (like todos.my_app) and a type. Items in a collection are owned by the author Atsign that created them and can be shared with other Atsigns.

Two ways to build a collection

There are two paths depending on what you want to store. Go to these next pages to continue your journey in AtCollections.

Collection item type	When to use
Create AtCollection from domain object	You have your own class (Todo, Pet, BlogPost)
Create AtCollection from Dart primitive	You just want to store a Map, String, or Uint8List

There are a bit of tiny things that differ between the two paths, but by the end of each path, both produce the same AtCollection<T> object which will be used to manage your collection of data. Everything after the initial setup (CRUD, sub-collections, read receipts, event streams) works the same way regardless of which path you took.